This invention relates in general to measuring devices and in particular to a new and useful device for facilitating the electro-chemical measurement of a substance such as a gas.
Electro-chemical measuring devices contain, as is known, an electrode system with at least two electrodes that are connected through an electrolytic layer and which are covered against the medium to be measured by means of a membrane that can be penetrated by a gas to be measured but cannot be penetrated by the electrolytes. The sensitivity of the electro-chemical analyzers depends on the condition of this separator membrane and the electrolytes. The electrolyte system must be renewed from time to time. This is done by changing the membrane and the electrolysis. For the most part this involves working with small parts. The electrolyte must be properly portioned, and dirt cannot be permitted. The membrane may have no wrinkles, and must be positioned and attached under a specific tension. All in all, this is a difficult and time-consuming procedure that cannot reliably be done, particularly by inexperienced persons, even at the measuring site. Even the use of known clamping devices in principle makes little difference.
In a known arrangement for changing membranes and electrolyte fillings in electro-chemical analyzers, the membranes are assembled in a replaceable capsule. By means of a screw-ring the capsule is maintained in contact with the analyzer before its electrodes. A portion of one electrode overhangs the other. As delivered, the capsule consists of a cup-shaped holder having a plastic-sheet floor that curves inward. The wall and the floor of the holder are covered with the membrane. The parts on the wall are closely connected by means of reinforcing rings and tension rings. The space between them and the curved floor is filled with electrolyte. When the capsule is put on, the floor is turned toward the electrodes. When the capsule is being screwed on with the screw-ring, the floor is penetrated by the projecting portion of one electrode; the overflowing electrolyte then moistens the electrodes. Flexible rings on the analyzer and screw-ring ensure the ouside seal after tightening and also the rigidity of the membrane. A disadvantage is that the storage time of the unused capsules is limited, because the electrolyte under the broad membrane is even subject to drying out than during operation if the membrane is completely covered by the screw-ring. When the capsule is installed, before penetration occurs the curved floor is distorted; the distortions, transmitted through the electrolyte filling, can lead to uncontrolled stretching of the membrane and can change the sensitivity of measurement through changes in its qualities. The foregoing electrode makes the analyzer unsuitable for many kinds of measure. The construction of the capsule of the capsule itself, and the loose screw-ring needed in addition, along with the sealing elements, is complicated and bothersome to handle.